I have a bluetooth headset (Logitech UE9000), I always found the sound quality on OSX to be less than when connected to my android phone.
Further investigation leads me to believe that there is no stereo sound being outputted. A simple youtube stereo test (e.g. https://www.youtube.com/watch?v=TAOQWSmkofA) has the result of left or right channel to be outputted simultaneously to both earspeakers.
This is not an quality issue, the sound is clear, as such, the advise which is littered everywhere on the web to up the quality by doing some command line magic is not helping:
defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Min (editable)" 200
By alt-clicking on the bluetooth icon I can see that my active codec is "AptX" which should be the correct codec for high quality.
Do others have successfully connected their headsets with real stereo/separate channel audio?